1. Field of the Invention
The present invention relates to a class of novel tin-containing organolithium compounds which can be used as anionic polymerization initiators and the preparation thereof. More particularly, the present invention relates to novel tin-containing organic monolithium compounds and bislithium compounds which can be used as anionic polymerization initiators and the preparation thereof.
2. Brief Description of Art
When used as anionic polymerization initiators, tin-containing organolithium compounds can produce polymers having, at each molecular chain end, a residual group derived from the initiators, a Sn-containing group, which is advantageous to the reduction in hysteresis of the polymers. U.S. Pat. No. 3,426,006 discloses a process for preparing trialkyltin lithium compounds by reacting 1 mole of stannous chloride with 3 moles of alkyl lithium; U.S. Pat. No. 5,268,439 discloses a process for preparing trialkyltin lithium compounds in one step by reacting a trialkyl tin halide with metallic lithium, but the resultant initiators have a relatively high content of ionic chloride; U.S. Pat. No. 5,502,129 discloses a process for preparing trialkyltin lithium compounds in two steps, aimed at reducing the content of ionic chloride. U.S. Pat. No. 5,877,336 discloses a process for preparing triorganotin lithium compounds by reacting metallic lithium with bis(triorganotin) in dimethyl ether at a temperature of 0 to 65xc2x0 C. and a pressure of 2 to 20 atms. The tin lithium compounds of the prior art are disadvantageous in that they have relatively poor solubility in solvents conventionally used for polymerization.
Since trialkyltin lithium compounds belong to monolithium compounds and contain only one active Snxe2x80x94Li bond, such compounds can generally be used to prepare linear polymers and if star polymers are desirable, coupling is necessary.
In terms of preparation of star polymers and simplification of the procedure for preparing block copolymers, organic bislithium compounds have advantages to which conventional monolithium compounds are incomparable. However, none of the adduct of divinyl benzene with monolithium compounds(EP 743 330A1), the adduct of bis(1,1-distyrene) type compounds with monolithium compounds(Quirk R. P., Ma Jing-Jing, Polymer International, 1991, 24(4), 197-206) and oligomeric lithium initiators(DD 150 149) contain, in addition to C, H and Li, other heteroatoms in the molecular chain, and it is well known that the presence of heteroatom Sn in the molecular chain is advantageous for the reduction in hysteresis of polymers.
Chinese Patent Application Publication No. CN 1 148 053A discloses a multifunctional organic alkali metal initiator having a Sn-containing functional group. Such initiators have a functionality of more than 2.5 and thus can only be used to synthesize star polymers.
A general object of the present invention is to provide a class of novel tin-containing organolithium compounds which are free of the disadvantages associated with the prior art and can be used as anionic polymerization initiators. Such compounds contain Sn atom and can be used to synthesize linear, star or telechelic polymers.
A specific object of the present invention is to provide novel tin-containing organic monolithium compounds which can be used as anionic polymerization initiators. Such compounds have good solubility in solvents conventionally used in anionic polymerization and its tin-containing group can retain at the molecular chain end of polymers prepared therewith, thereby reducing hysteresis of such polymers.
Another specific object of the present invention is to provide novel tin-containing organic bislithium compounds which can be used as anionic polymerization initiators. By using such compounds, the procedure for preparing block polymers can be simplified and the resultant polymers have a narrow molecular weight distribution and a high content of tin.
Another general object of the present invention is to provide a method for preparing the tin-containing organolithium compounds in accordance with the present invention.
These and other objects, features and advantages of the present invention will be apparent from the following description.
In its one aspect, the present invention provides a tin-containing organolithium compound which can be used as anionic polymerization initiators, represented by the following formula (1):
R4xe2x88x92xSn(Yaxe2x80x94Zmxe2x80x94Ybxe2x80x94Li)xxe2x80x83xe2x80x83(1)
wherein R represents C1-C20-alkyl, C3-C20-cycloalkyl or C6-C20-aryl or substituted aryl; Z represents straight or branched C1-C20 divalent hydrocarbon group, C6-C30-arylene or substituted arylene; Y represents a group derived from conjugated diene homopolymers, monovinyl aromatic hydrocarbon homopolymers or conjugated diene/monovinyl aromatic hydrocarbon copolymers; x represents a value of 1 or 2; m represents a value of 0 or 1; a represents a value of 0 to 6, b represents a value of 0 to 6, a+b is from 0 to 6, provided that m=1 when x=1.
In its another aspect, the present invention provides a method for preparing the tin-containing organolithium compound of formula (1).